DESCRIPTION (Taken directly from applicant's abstract) The long term goal of this research is to understand the molecular/genetic mechanisms involved in renal development and differentiation in order to develop new treatment modalities for chronic renal disease in pediatric patients. Specifically, an ideal therapy for chronic renal disease would be the induction of de novo nephrogenesis to repair the diseased kidney. We have characterized a unique vertebrate model of nephron replacement by neogenesis following renal injury in fish. Since nephron replacement following irreversible renal injury does not occur in mammals, it is essential to identify the genes required for nephron development to understand the genetic mechanisms which restrict mammalian nephrogenesis to embryonic development. Nephrogenesis in fish follows the same developmental pattern as renal development in mammals, suggesting the underlying genetic mechanisms are also similar. This model of mammalian renal development thus provides a unique system in which to identify novel nephrogenic genes. We hypothesize that novel nephrogenic genes, which have not yet been identified in mammalian systems, are induced during nephron neogenesis in fish and that conserved homologues of these genes play important roles in mammalian renal development. To characterize the fish nephrogenesis model of renal development at the molecular level, the expression of genes known to function in mammalian kidney development will be examined (Aim 1). To identify novel genes involved in nephrogenesis, cDNAs differentially expressed in control and nephrogenic goldfish kidneys will be isolated (Aim 2a). Nephrogenic genes identified in goldfish will be compared with those found in an aglomerular species, the toadfish; genes specifically involved in glomerular development will be identified by their lack of expression in this naturally occurring glomerulus knockout (Aim 2b). The sequence of isolated cDNAs will be compared for homology with known genes, and full length clones of novel cDNAs will be isolated from both fish and mammalian sources (Aim 3). The expression of nephrogenic genes during mammalian renal development will be analyzed in developing mouse embryos (Aim 4a). To directly examine the spatial and temporal regulation of novel nephrogenic genes, expression will be analyzed in developing mouse embryos and in nephrogenic goldfish kidneys by in situ hybridization (Aim 4b). The identification of novel nephrogenic genes in this study represents a requisite first step toward an understanding of the genetic mechanisms which function in nephron development and repair which may be defective in chronic renal diseases. This information will provide a foundation for the development of alternative renal replacement therapies based on the induction of entirely new nephrons in the injured kidney.